ABSTRACT- A series of studies have been conducted at the Seattle-Tacoma International Airport (STIA) to characterize the site-specific fate, bioavailability, and effects of copper (Cu) and zinc (Zn) in stormwater discharges. These studies include an evaluation of Zn fate and transport from the airport and other entities' storm drain discharges to forested wetlands, a stormwater retention facility, and a stream containing salmonids on STIA property. The fate and transport study also measured water quality parameters during multiple storm runoff periods for input to the biotic ligand model (BLM) and estimation of spatial and temporal variability in Zn bioavailability. Ongoing stormwater toxicity studies include acute whole effluent toxicity (WET) testing, 7-d rainbow trout embryo toxicity testing using in stream samples, and water effect ratio (WER) testing that will ultimately be used to develop site-specific water quality standards for Cu and Zn at the STIA. Results to date demonstrate that Cu and Zn concentrations in stormwater decline quickly before entering receiving waters at the site. The BLM-predicted WERs for Cu and Zn vary between 2 and 5 depending on location and timing during a storm. These studies will be used to provide a comprehensive evaluation of Cu and Zn fate and effects in receiving waters at the STIA.